August 9-15, 2019

This week was the slowest week yet this fall. Even so, 344 birds were banded and just as things seemed to be really slowing down, we caught 91 birds on August 14, bringing our total bands to 2,008 birds from 50 species. Since last week, Rose-breasted Grosbeaks have surpassed their previous fall banding record of 21 individuals with 22 banded. We now only need one more Western Tanager to have a record breaking season since they are currently tied with fall 2015 at 26 banded.

Pictured: Young Red-eyed Vireo hatched this year. Although it looks like an adult, it does not yet have the red eye of its namesake.

Remarkably, within the past week, we have captured at least one of each of the four vireo species that breed locally. Vireos are from the songbird family Vireonidae, which contains around 50 species across North and South America. Vireos are typically greenish and are easily misidentified as warblers due to their similar foraging behaviours and appearance. Vireos tend to have gray-blue legs and a heavier, slightly hooked bill where warbler species typically have yellow or black legs and narrow, needle-like bills that lack a hook. All four species of vireos found in northern Alberta rely heavily on insects for food and must migrate south for the winter. At one time, vireos were thought to be part of the warbler family, but new DNA evidence suggests they are in fact more closely related to corvids – the family of birds that includes crows, ravens, and blue jays.

Pictured: Fledgling Red-eyed Vireo captured this week that had only recently left the nest.

Red-eyed Vireos are our most common vireo species. They can be heard throughout the breeding season singing their brief two to three note song from the canopy, with some males recorded singing more than 20,000 times in a single day. It was only this week that this incessant song has quieted. Of the 32 Red-eyed Vireos that we have captured this fall, one of the most recent was a very young fledgling that was still actively being cared for by its parents. Other young Red-eyed Vireos are already self-sufficient and look very similar to adults, but they have not yet developed the red eye of their namesake.

Pictured: Philadelphia Vireo (photo from archives).

The Philadelphia Vireo sounds very similar to the Red-eyed Vireo, but with longer pauses between songs. As a result, they are often misidentified even by experienced birders. They are the most northerly breeding vireo species with 99% of their population breeding in Canada. So far this fall, we have banded eleven; all of them young birds.

Pictured: Blue-headed Vireo banded this week showing off how the hook to vireo bills can be used to hold onto flesh.

Blue-headed Vireos also sound similar to Red-eyed Vireos, but with a squeakier voice. Not only do they look different with their gray-blue head and white spectacles, they are also the only local vireo species that breeds in coniferous forests, although they will also make use of deciduous forests. We have banded two Blue-headed Vireos.

Pictured: Warbling Vireo (photo from our archives, we did not have time to get photos of the one we banded).

Although they look very similar to Philadelphia Vireos, Warbling Vireos have a unique husky warbling song that sets them apart from the other vireos. So far, we have only banded one Warbling Vireo.

To learn more about our local birds, join us on Wednesdays and Saturdays from 9 to 11 AM for bird observatory drop-in tours until the end of August.